The 1930 US Census of Huntington, Cabell Co., West Virginia, shows "Ford E. Cartmill" age 9 living with family including parents R.H. (Robert H.) and Ada C. Cartmill. Another of RH and Ada's children is Donald J. Cartmill, age 8.

The obituary of Donald J. Cartmill for June 4, 2007 states: DONALD JAMES CARTMILL, 85, husband of Evelyn Weber Cartmill, died Saturday, June 2 at St. Joseph Hospital. He was a native of Huntington W.Va., son of the late Robert Cartmill and Ada Nelson Cartmill Wheeler.

And indeed I find Ada Nelson, b abt 1899 in the 1910 US Census of Mccomas, Cabell Co, West Virginia, dau of Ferdinand & Jamie Nelson.

In searching for the social security death index, I find an Ada Wheeler (the same surname as shown in her son's death record) as shown below, born in 1899 (so the right year) and the only Ada Wheeler that seems to fit the profile. That SSDI says she died Feb 1984.

I haven't been able to find proof to support your theory of her death date. I did find an SSDI entry for an Ada Nelson that gives her death date as Feb 1984 but the location is Asheville, NC and the number was issued in New York so I doubt that is her. There is no entry for an Ada Cartmill in the SSDI.

The Feb 13 1899 date of birth for Ada Wheeler as given in the SSDI coincides with the same dob found in Ancestry World Tree for Ada Nelson (later Cartmill.) However, this date is not consistent with the Aug 1898 (or 1899) date given for Ada Nelson in the 1900 census. There are Huntington Adas listed in SSDI with names other than Cartmill who were born in either Aug of 98 and Aug of 99, but no evidence I can find that would tie any of them to Ada Nelson Cartmill, mother of Edsel Ford Cartmill.

Found obit for another of Ada Nelson Cartmill's sons: Donald James Cartmill - died at age 85. It listed his parents as Ada Nelson Cartmill Wheeler, so Ada's maiden names was Nelson and she remarried a Wheeler. I found a SS Death Index entry for Ada Wheeler in Cabell West Virginia. Shows birth date of 13 Feb 1899 and Death date of Feb 1984.Deb